1. Operating System Structure
Software architecture is a structure that makes the basis for determining the location of software components that interact with each other and the organization of components in forming an Operating System is the software in the first layer that is placed in the computer’s memory when the computer is activated and implanted in ROM. In the operating system there are also other softwares and operating systems tasked with running them. The piece of code that performs core and general tasks is called the “kernel” in an Operating System.
Operating System is the link between the hardware layer and the software layer. The Operating System also performs all important tasks in the computer, ensuring different applications can run simultaneously smoothly. If several applications are running simultaneously, then the Operating System that arranges scheduling appropriately, so that all running processes get enough time to use the processor (CPU) and not collide with each other.
In modern operating systems, a large and complex system has a structure that is designed carefully and thoroughly so that it can function as desired and can be modified by itself. The operating system structure is the components of the operating system that are connected and formed in the kernel.
- Simple Operating System Structure
The structure of this operating system that provides functional space in so little that it is not divided into modules, initials are limited to functional hardware which is divided into two parts, namely the kernel and the system program. The kernel is divided into a series of interfaces and device drivers and provides file systems, CPU scheduling, memory management, and other operating system functions through system calls.
• Service can be done quickly because it is in one room.
• Testing and eliminating errors is difficult because it cannot be separated and dialomatic.
• Difficult to provide security facilities.
• Waste of memory when every computer must run the kernel, because all services are stored in a single form while not all services are needed.
• Errors in some functions cause the system to malfunction. Examples of operating systems that have a simple structure are MSDOS and UNIX.
2. Structure of a Monolithic Operating System
The structure of a monolithic operating system is a simple structure that is equipped with dual-mode. The structure of the operating system in this system is unstructured. This type of operating system is defined as a collection of procedures where procedures can be invoked by other procedures in the system when needed. The kernel contains all services provided by the operating system to users. The operating system is written as a set of procedures, which can be called at any time by the user when needed. The basic structure of a monolithic system:
a. The main program that contacts the requested service procedures.
b. A collection of service procedures that provide system calls.
c. Collection of utility procedures that help service procedures.
• Services can be done very quickly because they are in one address space.
• Testing and eliminating errors is difficult because it cannot be separated and localized.
• Difficult to provide security facilities.
• It is a waste if every computer has to run a very large monolithic kernel while actually not requiring all the services provided by the kernel.
• Not flexible.
• Programming errors in one part of the kernel cause the whole system to shut down. Examples of operating systems that have a monolithic structure are the Linux Kernel and UNIX V7.
• Services in Operating Systems
- Making the program, the operating system simplifies and helps in accessing the debugger and editor processes that are already in the program in the form of utilities.
- Program execution, the operating system handles all user tasks. Tasks including data instructions must be loaded into memory, I / O devices must be initialized, including files must be initialized, and other resources must be stored.
- Accessing the I / O device, the device inside the I / O has its own instructions or signal control that is used for operations. The service provided by the operating system is to maintain the details so that programmers can think of it as a simple reading and writing operation.
- Controlled access to files, Controlled access is the file format contained in the storage media. furthermore the operating system provides a protection mechanism to control access to files.
- Detection of errors, Errors occur or errors in the computer are things that often occur. for example memory errors, overflow, device errors. etc. All errors that occur make the operating system must respond in order to eliminate the error, but little impact on the running application.
- Accounting, the operating system records all usage statistics of various resources and monitors performance parameters such as response time.